Grinding machine

ABSTRACT

This invention relates to a grinding machine and, more particularly, to apparatus for generating a surface of revolution by the abrasion process, wherein two hydraulic cylinders and a motor-driven screw are provided and combined to operate the machine in three distinct modes; controlled-force, controlledrate short-throw, and controlled-rate long-throw.

United States Patent [72] Inventors Herbert R. Uhtenwoldt Worcester;

Frederick A. Hohler, Holden; Richard T. Knorring, Worcester, all of, Mass.

[2]] Appl. No. 763.294

[22] Filed Sept. 27, 1968 [45] Patented July 20, 1971 [73] Assignee The Heald Machine Company Worcester, Mass.

[54] GRINDING MACHINE 9 Claims, 8 Drawing Figs.

[52] U.S.Cl 5l/l65.8, 51/l65.9 [51] Int. Cl B24b 49/08 [50] Field ofSearch 51/165,

I 56] References Cited UNITED STATES PATENTS 2,486,244 10/1949 Balsiger et a1. 2,657,505 1 H1953 Price 3,197,921 8/1965 Hohler et al. 3,407,543 10/1968 Gebel Primary Examiner Lester M. Swingle Attorney-Norman S. Blodgett ABSTRACT: This invention relates to a grinding machine and, more particularly, to apparatus for generating a surface of revolution by the abrasion process, wherein two hydraulic cylinders and a motor-driven screw are provided and combined to operate the machine in three distinct modes; controlled-force, controlled-rate short-throw, and controlled-rate long-throw.

PATENTEUJULZOMYI 3,593,463

SHEET 1 [IF 6 FIG. I

HERBERT R. UHTENWOLDT FREDERICK A. HOHLER RICHARD T'. KNORR/NG INVENTORS.

PATENTEU JUL20 IBYI SHEE 2 F 6 llllllll ll zsa PATENTEU JUL20 i971 sum 3 OF 6 PATENTEU JULZO 1971 SHEET 5 OF 6 Q 0 0 83m unm ou 52o QEIVESS 55.32: 6528 2mm Elsie? mwwzaou 3% 12m 6:; Erin um; new

tum; $2.53

PIG: Z0 KUZOA TABLE OUT RAPID TRAKERSE TABLE IN (6) RAPID BACKOFF, DAMPER BY-PASS, RESET TO ZERO 8 RET. GAGE ROUGH SPARKOUT RETRACT/ON REsET FINE FEED RATE 2nd SIZE RETRACTION FINAL GAGE 0R SIZE SLIDE COMPENSATE S CONTROLLED BACK-OFF DREssER DowN (IF usED) TABLE IN DRESS SPEED TRA VERSE\ INTERMEDIATE GAGE OR 2nd SIZE, STOP FEED UNLOAD [LOAD DRESSER RESE T DRESSER ROTATE DAMPER IN, CONTROLLED FORCE 8 RETRACTION FRONT C SLIDE AGAINST STOP RELEAsE GA GE (IF usED) FIG. 7

DRESS AT RUNOUT CYCLE TABLE OUT RAPID TRAVERSE UNLOAD LOAD j' I N DRESSER sIDE COMPENSATE AND TABLE OUT@ BACKOFF DAMP RAP) TRAVERSE CONTROLLED BAG/:(OFF ER BY-PAss, TABLE IN E L RESET To G QAPID TRAVERSE TABLE IN@ DREss sPEED DREssER D0wN zERo RETRAcT GAGE BACKOFF, DAMPER BY-PASS, RESET TO zERo, RETRAcTIoN DAMPE R IN, CONTROLLED FoRcE SLIDE AGAINST STOP RAPID RESET TO DRESS POSITION FINE FEED RATE J INTERMEDIATE GAGE OR 2nd SIZE, STOP FEED L 2nd SIZE RE TRAC TION FINISH SPARKOUT FINAL GAGE OR SIZE INTERRUPT FOR DRESS TABLE WE T IF USED) DREs'sER ROTATE IN (1') RARE TRAVERSE DAMPER IN, CONTROLLED FORCE a RETRACTION FRONT SLIDE AGAINST STOP, RELEASE GAGE (IF USED) INTERMEDIATE FEED RATE GAGE CYCLE DRESS SIGNAL-GAGE OR SIZE STOP FEED CYCLE GRINDING MACHINE BACKGROUND OF THE-INVENTION In the design and operation of grinding machines and, particularly, those used in internal grinding, it has been common practice to provide for two types of erossfeed of the abrasive wheel into the work. One type of feed, called the controlledrate" method, usually uses a nut-and-screw arrangement in which the relative motion between the wheelhead and the workhead takes place with a controlled rate and the force between the abrasive wheel and the workpiece varies accordingly. The second method of feed, called the controlledforce" method, makes use of a hydraulic cylinder, so that the force between the abrasive wheel and the workpiece is determined by the pressure of the fluid in the cylinder, but the rate movement between the wheelhead and the workhead varies. Some machines have been designed and built which provide both of these methods of feed in the same machine, so that the machine is capable of grinding the workpiece alternatively with controlled-force, with controlled-rate, or with a cycle using the combined feed is a cycle in which the roughing portion of the cycle takes place under controlled-force conditions for the rounding-up of the workpiece, followed by the removal of the wheel for a dressing operation, and then the wheel is reinserted for grinding in a finishing portion of the cycle using controlled-rate feed.

It has recently been discovered that the controlled-rate portion of the cycle may be beneficially brought about by rotating the screw by means of a stepping motor, this being the type of motor in which a small incremental rotation of the motor takes place upon the receipt of a single electrical pulse; the stepping motor combined with suitable electronic controls can rotate the feed screw in either direction by exact predetermined amounts. However, with present electronic equipment, it has been found possible only to generate pulses at rates in the order of 200 pulses per second. This means that, if one wishes to use such a combination" machine in situations where controlled-rate method is to be used for long grinds even during the roughing portion of the cycle, the retraction of the wheel for dress and after the grinding of a workpiece takes a very long time. The problem is particularly acute when the wheel has been completely worn out and the operator wishes to move the machine forward to a new wheel" position. In other words, none of the prior art machines are capable of operating with controlled-force combined with shortstroke controlled-rate (or with long-stroke controlled-rate), particularly where the controlled-rate during finish grinding makes use of stepping motors controlled by countable pulses. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a grinding machine capable of controlled-force feed, controlled-rate feed, and of providing grinding cycles combining these two types of feed.

Another object of this invention is the provision of a grinding machine having two interrelated controlled-rate feed means, one being intended for long-stroke feed and the other for very accurate short-stroke feed.

A further object of the present invention is the provision of a grinding machine capable of carrying out combined cycles of controlled-force and controlled-rate grinding without long periods ofnonmachining movement.

It is another object of the instant invention to provide a grinding machine capable of complex grinding cycles which is inexpensive to manufacture, which is simple and rugged in construction, and which is capable ofa long life of useful service with a minimum of maintenance.

A still further object of the invention is the provision of a grinding machine having an element which operates as a damper during controlled-force grinding and operates as a regulator during controlled-rate grinding.

It is a further object of the invention to provide a grinding machine capable of complex grinding cycles but making use of relatively simple and inexpensive actuators.

It is a still further object of the present invention to provide a grinding machine having hydraulic means for controlledforce grinding, long-stroke controlled-rate grinding, operatively combined with electrical means for short-stroke, controlled-rate grinding.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In general, the invention consists ofa grinding machine having a base, having a wheelhead table mounted on the base, having a workhead table mounted on the base, and having means connecting one of the tables to the base to bring about transverse feeding movement between the tables, including a first cylinder, a second cylinder, and a screw-operated stop. The first and second cylinders are operative for controlledforce feeding. The second cylinder and the stop are operative for short stroke controlled-rate feeding, while the first and second cylinders are operative for long stroke controlled-rate feeding.

More specifically, a throttling circuit connects the ends of the second cylinder and the throttling aperture is adjustable to a large size for use during the controlled-force feeding and the short-stroke controlled-rate feeding and to a small size for use during the long-stroke controlled-rate feeding. The stop is movable relative to the base by means of a ball-and-serew arrangernent, the screw being rotated in very accurate increments by a stepping motor. A dependent portion of the table extends downwardly for contact with the stop. The stepping motor operates on the stop during every grinding cycle to determine the amount of feeding, retraction for dress, and compensation for dress, as well as to reset the stop for a new wheel.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. I is a perspectiveview of a grinding machine embodying the principles of the present invention,

FIG. 2 is a rear perspective view of the machine,

FIG. 3 is a sectional view through a portion of the machine taken on the line IIIIII of FIG. .4,

FIG. 4 is a plan view ofa portion of the machine,

FIG. 5 is a sectional view through a portion of the machine taken on the line V-V of FIG. 4,

FIG. 6 is an enlarged portion of the control panels associated with the machine, and

FIGS. 7 and 8 are diagrams of grinding cycles that may be performed by use of the machine.

Referringfirst to FIG. I, wherein are best shown the general features of the invention, the grinding machine, indicated generally by the reference numeral 10, is shown as consisting ofa base II on which is mounted a wheelhead table I2. Also mounted on the base is a workhead table 13 adapted to carry a workhead 14 of the type shown and described in the US. Pat. of Townsend et al. No. 3,l3l,5l7 at FIG. 7, and shown and described in the copending application of Hohler et al., Ser. No. 763,295, filed Sept. 27, I968 Mounted on the base 11 and overlying the tables is a control box I5. Mounted on the wheelhead table is a wheelhead l6 driven by a motor 17 and having a spindle 18 on the other end of which is mounted an abrasive wheel 19. The wheelhead table I2 is mounted on the base for movement longitudinally'of the axis of the spindle 18 under the control of suitable dogs 21 operating on reversing valves 22 and the like in the well-known manner. The workhead table I3 is mounted for sliding movement transversely of the spindle axis, as will be described more fully hereinafter.

FIG. 2 shows the rear of the machine and doors 2 3 and 24 which give access to the control box 15. Underlying the control box are various control valves 25 and 26. Also, at the rear of the machine is the hydraulic fluid pump 27 mounted on the upper surface ofa tank 28 and driven by a motor 29.

FIGS. 3,4, and show the manner in which the workhead 13 is mounted and moved for a feeding operation. A lower element 31 is bolted to the base 11 and, for purposes of discussion, will be considered part of the base. Extending upwardly from the lower element 31 are rails 32 and 33, while the table 13 is provided with a way element 34 which cooperates with the rails 32 and 33 to form hydrostatic ways in the manner shown and described in the copending application of Uhtenwoldt, Ser. No. 729,690, filed May l6, l968, now Pat. No. 3512,848, dated May I9, 1970. This is a self-balancing hydrostatic bearing which assures that, when the forces on the workhead table 13 (either in the horizontal or vertical direction) increase and decrease, the thickness of the oil film between the bearing surfaces does not change, so that movement does not take place in that direction.

Slidable transversely relative to the lower element 31 is a block 35 having a forwardly directed shaft 36 which is slidably mounted in a ball bearing 37 mounted in a suitable flange of the lower element 31. The rear of the block 35 is provided with two flanges 38 and 39 carrying ball bearings 41 and 42,

v respectively. In the bearing 41 is carried a shaft 43, while a similar shaft 44 extends through the bearing 42. Both of these shafts are mounted on suitable flanges connected to the lower element 31. The block 35 is formed with an upwardly directed recess 45 having facing vertical surfaces 46 and 47. Extending from the surface 46 is a contact member 48 which has a threaded adjustment in the shaft 36. This threaded adjustment takes place by means ofa knob 49 which is accessible from the front of the machine and can be seen in FIG. 1. The surface 47 is provided with a fixed contact member 51. Mounted in the rear of the block 35 is a nut 52 which is engaged with a screw 53, the two making up a ball-type screw-and-nut arrangement of the well-known type. The screw is mounted in a roller bearing 54 and carries at its outer end a gear 55 operably engaged by a worm 56 which, in turn, is rotated by a stepping motor 57 (see FIG. 4).

Extending downwardly from the table 13 and, more specifically, from the way element 34, is a finger 58 having a plate 50 adapted to make contact with the contact member 48 and carrying an electrical sensing element 61. On the opposite side of the finger 58 facing the surface 47 is a contact plate 62 in which is embedded an electrical sensing element 63. The sensing elements 61 and 63 indicate very accurately the point of engagement of their respective contact plates with the ad jacent contact members and indicate this fact to the control circuits.

Mounted on the front of the base or lower element 31 is a cylinder 64 having ports 65 and 66 at the ends. The bore of the cylinder is of relatively small diameter and carries a piston 67. The piston is provided with a piston rod 68 whose other end is connected to the table 13. The intermediate portion of the piston rod 68 is provided with a large piston 69 which is slidable in the bore of a cylinder 71 which is also bolted to the base element 31. The ends of the cylinder 71 are provided with ports 72 and 73 which are connected by a conduit 74 in which is located a variable orifice 75 which is adjustable by means of a knob 76.

As is evident in FIG. 4, the wheelhead table 12 is provided with a hydraulic cylinder 77 to produce longitudinal motion and with an oscillator 78 to produce longitudinal oscillation of the wheel 19 in the workpiece during grinding.

FIG. 6 shows the details ol'the control panel. A gage unit 79 is provided for use when the sizing of the workpiece bore and the control ofthe machine takes place by use ofa gage located in the bore of the workpiece, and this unit includes means for setting the gages and setting various intermediate controls as well as final size and meters indicating the progress of the grinding operation. The control panel also includes indicator lights 81 which show by means of lights whether the electrical power is on the machine, when the table floats because of the maintenance ofa hydrostatic film, when it is time to change an oil filter, when the wheelhead table 12 is out, and when the wheelhead table is in. The lights also show when the workhead table 13 is against the stop 51, when the first size of the bore is reached, when dress is taking place, when the second size of the bore is reached, and when the final size of the bore is reached. The lights also show when the diamond is being turned, when there is no part in the machine, when the wheel has been worn to a useless size, when a new wheel position has been reached in the machine, and when the wheel has been dressed down to its operative size after the conclusion of a new wheel cycle. The dressing apparatus 82 is mounted on the workhead table 13.

The next row 83 of switches includes a starting pushbutton for the main drive, a pushbutton to start the wheelhead motor 17, a pushbutton to start the workhead motor (not shown), a switch to put the coolant pump in either of or on on position, a switch for operating the dressing apparatus, either for hand operation or for automatic operation, and a switch for indicating that the cross-slide is either on automatic," off, or reset" condition. The next row 84 of switches includes a pushbutton for stopping the main drive, a pushbutton for stopping the wheelhead motor 17, a pushbutton for stopping the workhead motor, a two-position switch for putting the oscillator 17 either on or "off, a three-position switch for putting the dresser 82 either on up," down," or *automatic" condition, and a switch for use in the cross-slide to move it under manual control either to the rear or to the front, this last switch being spring centered, so that, when the operator is not using it, it is in neutral position. The next row 85 of switches includes a selector switch for selecting whether the machine will operate by the so-called Gagematid system, by the "Sizematic" system, or whether it is in off" position. This row also includes a switch for selecting a cycle in which the dress takes place at runout, or takes place by an interruption of the grinding. Finally, a switch is provided in that row for selecting the condition of the cross-slide toward a backoff position, a grind position, or an automatic position; this latter switch is spring centered, so that it stays in automatic position unless manually moved to one of the other two positions.

The next row 86 includes a selector switch for placing the grinding cycle on hand," off, or automatic" condition, a switch for the interlock as being either in off or on" position, a gage switch for placing the gage in either single, double," or of condition, a switch for placing the skip-dress apparatus either in "off" or on" condition, and a switch for providing for the grinding force to be either low, high," or automatic.

The next row 87 includes a pushbutton for causing the table to go in, and a switch for allowing the machine to operate with no part, this last switch being either in off" or on" condition. A switch is also located in the row 87 for placing the gage either in setup, off,", or automatic" condition, and a spring-centered switch for placing the diamond turner either in automatic, off," or turn" condition.

The bottom row 88 includes a table-out pushbutton, and a loading pushbutton, as well as an emergency stop switch. The panel 89 associated with the control of the stepping motor 57 includes a load meter 91 and a skip-dress counter 92. A row 93 includes dialable elements for setting the rate of pulse transmittal to the motor, one of them being set for the rough grind portion of the cycle, another for the intermediate rate and one for a fine rate of feed, it being understood that the larger the number the slower the feed rate and vice versa.

The next row 94 allows for setting the amount of total movement of the wheelhead table during certain parts of the cycle including the amount of a coarse compensation after dress, an amount of normal compensation after dress, an amount of retract, and the amount of second size retract.

The next row 95 includes a set of timers, one for timing the amount of time that low-force grinding takes place, another for determining the length of time that a rough sparkout takes place, another for the length of time that a finish sparkout takes place, and another for the length of time that no part is in the machine. Finally, in this same row is located a speed control for a workhead used when miniature bearing races and the like including workpieces having small bores are being ground.

The final panel 86 includes indicators and control elements having to do with the condition of the abrasive wheel 19. Across the top row are lights showing when coarse dress, wheel size, wheel wear, and slide reset are taking place in the machine. The bottom row provides settings for the amount of the coarse dress, the total of dress on the new wheel, the total wheel wear allowable before the wheel is changed, and finally, the wheel size at any given time as compared to the total wheel wear allowable.

The operation of the apparatus will be best understood in connection with grinding cycles that can be used with the machine. For instance, in FIG. 7 is shown'a cycle in which the dressing of the wheel takes place while the loading operation is taking place in the workhead. This is the point A where the wheel 19 has been withdrawn from the workpiece and the wheelhead table 12 has been moved to its furthest position to the right. At the start of the cycles, the cylinder 77 is actuated to move the table in from the point A to the point B using dress speed at first and then at rapid traverse speed. Oil is introduced through the port 66 to the cylinder 64 to carry the the table forward on a rough grind to the point C. The throttle valve 75 is set with an open orifice so that the piston 69 simply acts as a damper to remove objectionable vibrations or unwanted movements from the feed cycle and it acts as a damper. In this forward movement of the table 13, the finger 58 eventually engage the contact member 48 for a stop condition. The gage, if used, is placed in operation and the wheel continues to grind on a rough sparkout to a point D. Eventually, the oil is reversed in the cylinder 64. The table is moved backwardly to the point E on a retraction reset, the contact member 51 engaging the finger 58 at that point. Then, the table 13 is moved forwardly again on a fine feed to the stop point F, as determined either by the gage or by a second size feed stop. There is a second size retraction to the point C and, finally, forward movement of the table to the final gage or size at the point H. There is a transverse backoff of the table to the point I and then a longitudinal movement of the wheelhead table 12 to the point J where loading and dressing take place. At that point, slide compensation takes place. If the basic wheel is an annular wheel, as would be used in a plunge grind for a ball bearing race groove, the dresser would be rotated, while the table stays in fixed position. With a cylindrical wheel and dress, the dresser is brought down ready for the workpiece to be dressed as the table moves in from the point A to the point B.

Another typical grinding cycle for dress is shown in FIG. 8. Starting at point A, where the wheelhead table 12 is at its extreme right position and a new workpiece is in the workhead, the cylinder 77 is actuated to move the table in on a rapid traverse to the point B where the wheel 19 lies within the workpiece bore. Pressure fluid is applied to the cylinder 64 to move the table 13 forward to produce a controlled-force grinding operation. The cylinder 71 has its valve 75 set with a large orifice to act as a damper, and this action takes place to the point C where the contact plate 59 strikes the contact member 48 and a signal is received in the sensing element 61 to indicate that that contact has been made. Ifa gage is used in the cycle to control size, this gage is set in operation at that time. The table then moves forward at an intermediated feed rate determined by the operation of the stepping motor 57 moving the whole block 35 toward the front of the machine and allowing the table 13 to follow it. This takes place at controlled-rate until the point D is reached. The last part of this feed takes place by a rough sparkout until the gage indicates that the dress size is reached at the point D. At that time, the table 13 is moved rearwardly by reversing the fluid to the cylinder 64 and the table moves back until contact is made between the contact member 51 and the contact plate 62 at the point E. The cylinder 77 is actuated to move the wheelhead table 12 to the right on a rapid traverse to the point F. At that time, the stepping motor produces compensation and the dresser is run down. The fluid to the cylinder 77 is reversed to bring the table to the left at a dress speed and, finally, by rapid traverse to the point G. Another controlled-force grind takes place to the point H until the finger 58 of the table 13 again engages the forward contact member 48. There is a rapid reset to dress potion of the point I and then movement takes place at a fine feed rate (controlled-rate) to the point J, as indicated by the gage. Feed is stopped and there is a second size retraction to the point K and a finish sparkout due to any remaining deflection in the spindle 18 to the point L, this being the final size as indicated by a in-process gage. At that point, the table 13 is backed off to the point M and the wheelhead table 12 is moved to the right to the point N where the unloading and i loading operations take place.

Now, a study of theses two cycles that have been shown indicates that a portion of the grinding takes place by controlled-force feed under the impetus of the cylinder 63 with the cylinder 71 acting as a damper. Another portion of the grinding takes place at controlled-rate feed with the contact member 48 walking away from the finger 58 under the movement of the block 35 brought about by the stepping motor 57. The cylinder 64 only serves to keep the contact plate 59 in contact with the contact member 48 so that the table I3 follows the block 35. However, the controlled ate feeding that takes place in this manner is capable of being used only where the feeding is for small portions of the total grinding away of the workpiece. If, however, it is desired to use controlled-rate feed for larger portions of the grinding cycle, then the fact that the stepping motor 57 can be reversed only at relatively low speeds (because of the inherent limitation on the number of pulses that can be generated and controlled by the electronic circuitry with present-day stepping motor controls), another method of controlled-rate feed is desirable. For this purpose, the block 35 and the contact member 48 are kept out of contact with the finger 58 and the motion takes place under the impetus of the cylinder 64 but with the valve 75 of the cylinder 71 shut down to give a very small orifice. At that time, the kind of grinding which takes place is controlled-rate grinding because the table 13 can move forward only when oil has flowed from one side of the piston 69 to the other through the conduit 74. In other words, the rate of feed is determined by the rate of flow of fluid from one side of the piston 69 to the other through the conduit 74. In other words, the rate of feed is determined by the rate of flow of fluid from one side of the piston to the other. This, of course, is not as fine a rate control as is possible by use of the stepping motor, but is permits expanding the feed-rate portions of the cycle without running into the problem of long recovery times when the stepping motor is reversed.

It is possible, therefore, by use of the present invention to set up a wide variety of cycles, sizes of workpieces, and amounts of grind by using the various methods of feed. To review, the table 13 can be moved forwardly with controlledforce grinding by using the cylinder 64 and using the cylinder 7l only as a damper with the valve 75 in a fairly open position with a large orifice. Controlled-rate feeding can take place by maintaining the contact plate 59 of the finger 68 of the table 13 in engagement with the contact member 48 associated with the block 35; this block is then walked forwardly by the stepping motor and the rate of feed of pulses through the stepping motor determines the rate in which grinding takes place. This, however, can only be used with short stroke controlled-rate grinding. Finally, controlled-rate feeding for long stroke can take place by disengaging the block 35 from the finger 58 and using the cylinder 64 for the actuator but using the cylinder 71 with the valve 75 shut down to give a small orifice as the rate-regulating feature.

it is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is'not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what we claim as new and desired to secure by Letters patent is:

l. A grinding machine, comprising a. a base,

b. a wheelhead table mounted on the base,

c. a workhead table mounted on the base,

(1. means connecting one of the tables to the base to being about transverse feeding movement between the tables, including a first cylinder, a second cylinder, and a screwoperated, stop, the first and second cylinders being mounted in series, directly connected between the said one of the tables and the base, and being operative for controlled-force feeding, the second cylinder and the stop being operative for short-stroke controlled-rate feeding, while the first and second cylinders are operative for long-stroke controlled-rate feeding.

2. A grinding machine, comprising a. a base,

b. a wheelhead table mounted on the base,

c. a workhead table mounted on the base, and

d. means connecting one of the tables to the base to bring about transverse feeding movement between the tables, the said means including a first cylinder and piston of small diameter to produce controlled-force feeding and second cylinder and piston of relatively large diameter having a throttling circuit between the ends of the second cylinder to produce low-pressure fluid damping.

3. A grinding machine, comprising a. a base,

b. a wheelhead table mounted on the base,

c. a workhead table mounted on the base,

d. means connecting one of the tables to the base to bring about transverse feeding movement between the tables, including a first cylinder, a second cylinder, and a screwoperated stop, the first and second cylinders being operative for controlled-force feeding, the second cylinder and the stop being operative for short-stroke controlled'feeding, while the first and second cylinders are operative for long-stroke controlled-rate feeding,

e. a throttling circuit connecting the ends of'the second cylinder, and

f. a throttling aperture, adjustable to a large size for use during the controlled-force feeding and the short-stroke controlled-rate feeding and to a small size for use during the long-stroke controlled-rate feeding.

I 4. A grinding machine as recited in claim 3, wherein the first cylinder has a relatively small diameter, while the second cylinder has a relatively large diameter.

5. A grinding machine, comprising a. a base,

b. a wheelhead table mounted on the base,

c. a workhead table mounted on the base,

d. means connecting one of the tables to the base to bring about transverse feeding movement between the tables, including a first cylinder, a second cylinder, and a screwoperated stop, said stop being moveable relative to the base by means of a ball-and-screw arrangement, the screw being rotated in very accurate increments by a stepping motor and wherein a finger portion of the said one of the tables extends downwardly for contact with the stop, the first and second cylinders being operative for controlled-force feeding, the second cylinder and the stop being operative for shortstroke controlled-rate feeding, while the first and second cylinders are operative for long-stroke controlled-rate feeding.

6. A grinding machine as recited in claim 5, wherein the stepping motor operates on the sto during every grinding cycle to determine the amount offec ing, retraction for dress, and compensation for dress, as well as to reset the stop for a new wheel.

7. A grinding machine as recited in claim 5, wherein the stop is in the form ofa block having a forwardly directed shaft slidable in a bearing mounted on the base in alignment with the ball-and-screw arrangement and having two rearwardly directed shafts similarly slidable in bearings mounted on the base on opposite sides of the ball-and-screw arrangement.

8. A grinding machine as recited in claim 7, wherein the stop has an upwardly directed recess having two facing vertical surfaces, wherein the finger portion of the said one of the tables extends into the recess and has contact plates facing forwardly and rearwardly toward the said surfaces, and wherein each surface has a contact element extending toward a contact plate.

9. A grinding machine as recited in claim 5, wherein the said one of the tables is mounted on hydrostatic ways for transverse feeding movement. 

1. A grinding machine, comprising a. a base, b. a wheelhead table mounted on the base, c. a workhead table mounted on the base, d. means connecting one of the tables to the base to being about transverse feeding movement between the tables, including a first cylinder, a second cylinder, and a screw-operated, stop, the first and second cylinders being mounted in series, directly connected between the said one of the tables and the base, and being operative for controlled-force feeding, the second cylinder and the stop being operative for short-stroke controlled-rate feeding, while the first and second cylinders are operative for long-stroke controlled-rate feeding.
 2. A grinding machine, comprising a. a base, b. a wheelhead table mounted on the base, c. a workhead table mounted on the base, and d. means connecting one of the tables to the base to bring about transverse feeding movement between the tables, the said means including a first cylinder and piston of small diameter to produce controlled-force feeding and second cylinder and piston of relatively large diameter having a throttling circuit between the ends of the second cylinder to produce low-pressure fluid damping.
 3. A grinding machine, comprising a. a base, b. a wheelhead table mounted on the base, c. a workhead table mounted on the base, d. means connecting one of the tables to the base to bring about transverse feeding movement between the tables, including a first cylinder, a second cylinder, and a screw-operated stop, the first and second cylinders being operative for controlled-force feeding, the second cylinder and the stop being operative for short-stroke controlled-feeding, while the first and second cylinders are operative for long-stroke controlled-rate feeding, e. a throttling circuit connecting the ends of the second cylinder, and f. a throttling aperture, adjustable to a large size for use during the controlled-force feeding and the short-stroke controlled-rate feeding and to a small size for use during the long-stroke controlled-rate feeding.
 4. A grinding machine as recited in claim 3, wherein the first cylinder has a relatively small diameter, while the second cylinder has a relatively large diameter.
 5. A grinding machine, comprising a. a base, b. a wheelhead table mounted on the base, c. a workhead table mounted on the base, d. means connecting one of the tables to the base to bring about transverse feeding movement between the tables, including a first cylinder, a second cylinder, and a screw-operated stop, said stop being moveable relative to the base by means of a ball-and-screw arrangement, the screw being rotated in very accurate increments by a stepping motor and wherein a finger portion of the said one of the tables extends downwardly for contact with the stop, the first and second cylinders being operative for controlled-force feeding, the second cylinder and the stop being operative for short-stroke controlled-rate feeding, while the first and second cylinders are operative for long-stroke controlled-rate feeding.
 6. A grinding machine as recited in claim 5, wherein the stepping motor operates on the stop during every grinding cycle to determine the amount of feeding, retraction for dress, and compensation for dress, as well as to reset the stop for a new wheel.
 7. A grinding machine as recited in claim 5, wherein the stop is in the form of a block having a forwardly directed shaft slidable in a bearing mounted on the base in alignment with the ball-and-screw arrangement and having two rearwardly directed shafts similarly slidable in bearings mounted on the base on opposite sides of the ball-and-screw arrangement.
 8. A grinding machine as recited in claim 7, wherein the stop has an upwardly directed recess having two facing vertical surfaces, wherein the finger portion of the said one of the tables extends into the recess and has contact plates facing forwardly and rearwardly toward the said surfaces, and wherein each surface has a contact element extending toward a contact plate.
 9. A grinding machine as recited in claim 5, wherein the said one of the tables is mounted on hydrostatic ways for transverse feeding movement. 